Anti-detonating carburetor



United States Patent 2,747,561 Fatented May 29, 1956 ice 2,747,561 AurenEroNArnJo CARBURETOR Howard H. Dietrich, Rochester, N. Y., assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application May 6, 1954, Serial No. 423,075

11 (Ilairns. (Cl. 123-119) This invention pertains to means for preventing destructive detonation in internal combustion engines, and particularly to means for automatically sensing incipient deterticn and thereafter preventing the occurrence of destructive detonation.

At the pres nt time, compression ratios in internal combustion eng 3 for motor vehicles are limited by the knock characteristics of commercially available fuels. However, if detonation could be prevented to an appreciable extent with the use of commercial fuels, the compression ratio could be increased progressively for given fuel characteristics up to the considered optimum value of approximately 12 to 1, above which further increase in the compression ratio will increase engine efficiency to pro ressively diminishing extent; to the point where further increas in compression ratio may not be desirable. This invention relates to an improved antidet-onating cturetor of the general type disclosed in my copending application, Serial No. 410,284, filed February 15, 1954. Accordingly, among my objects are the provision of means for sensing incipient engine detonation; the further provision of a carburetor including means for automatically enriching the mixture when conditions are such that detonation is likely to occur; and the still further provision of incipient detonation sensing means, the operation or" which is automatically modified in accordance with elapsed ti ie of engine operation.

The aforementioned and other objects are accompushed in the present invention by incorporating means f r sensing incipient engine detonation in response to throttle position, carom or venturi depression or engine intake vacuum, in (Lille temperature, mixture humidity, and elapsed time or engine operation, which is a criterion indicative of carbon ZlCCUiTiulfllIlOIl in a given engine. Since it has been determined that detonation in an engine is a function of the aforementioned parameters, the sensing means must be responsive to predetermined conditions of the various parar. eters so as to enrich the mixture at the proper time to prevent destructive detonation.

In the carburetor disclosed herein, a solenoid operated fuel val e, submerged in the fuel reservoir, controls an auxiliary orifice for permitting fuel how to the carburetor arranged in bucking relationship. The bucking relay coils are magnetically associated with an armature operable to com lete the energizing circuit for the solenoid when ever a predetermined current differential exists between the two parallel circuits.

Each parallel circuit is connected between a source of direct current voltage, which may be the vehicle battery, and ground, through a throttle position controlled switch. The throttle positioned cc' troi switch is open when the throttle is closed, and is clcscd when the throttle is moved to a predetei position. One of the parallel circuits in ble resistor, the ohmic value of the moisture content of the intake mixthe ohmic value of which varies with the temperature of the intake manifold mixture; and

a non-linear variable resistor, the ohmic value of which is controlled by either venturi pressure or engine intake vacuum, these elements being serially connected with one of the bucking relay coils. The other parallel circuit includes a manually variable calibratim resistor and a variable resistor, the ohmic value of which changes with the elapse of time, and is, therefore, indicative of the elapsed time of engine operation, these elements, likewise, being serially connected with the other bucking relay coil.

Inasmuch as the throttle position controlled switch energizes the parallel circuits whenever the throttle valve is moved to, or past, a predetermined open position, when a predetermined current differential exists in the parallel circuits, which phenomenon occurs when incipient detonation is sensed, the solenoid will be energized so as to effect an enrichment of the air-fuel mixture supplied to the engine. In this manner, and in accordance with well recognized principles, destructive detonation will be prevented.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred embodiment of the present invention is clearly shown.

The drawing represents a schematic diagram of the antl-detonating carburetor of this invention.

With particular reference to the drawing, a carburetor it is shown having a throttle control outlet passage 11 which communicates with intake passage 12. According to conventional practice, the carburetor includes a venturi 13 and a float valve controlled fuel reservoir 14. The fuel reservoir 14 and the throat of the venturi 13 are interconnected by a nozzle and a tube 15' having a Y-connection submerged within the fuel reservoir. One leg 16 of the Y carries a metered main fuel orifice 17 through which fuel may be admitted to the fuel reservoir to the venturi throat in a conventional manner. The other leg 13 contains a metered auxiliary orifice 19, communication between the orifice 1? and the fuel reservoir being controlled by a solenoid operated disc valve 29.

The solenoid operated disc valve 2% includes a plunger 21, which is biased by a spring 22 that normally maintains the disc valve closed, thereby blocking communication between orifice l9 and the fuel reservoir 14. The plunger 21 is coaxially disposed within a housing 23 within which a solenoid winding 24 is located. One end of the solenoid winding 24 is connected to ground, and the other end of the solenoid winding is connected by wire 25 to a relay contact 25. From the foregoing, it will be appreciated that whenever the solenoid winding 24 is energized, the plunger 21 will move to the right, as viewed in the drawing, whereupon the disc valve 20 will permit communication between the auxiliary orifice 19 and the fuel reservoir 14 so that air flowing through the venturi 13 may pics up fuel from the nozzle through both orifices 18 and 39. In this manner, the mixture passing through the carburetor outlet 11 and into the intake passage 12 will be enriched.

The carburetor Ill is formed with a passage 27 having connection with the throat of the venturi 13. Accordingly, passage 27 will sense venturi pressure, or in other words, it will be a measure of air flow through the carburetor to the engine. The passage 27 is connected by a conduit 23 to a suction motor, designated generally by the numeral 3%. The suction motor 30 comprises a housing 31 of generally cup-shaped configuration, the open end of which is closed by a flexible diaphragm 32. The diaphragm 32 constitutes one seat for a coil spring 33, the other end of the spring 33 being seated in a cup-shaped member 34, which is carried by a stud 35 that threadedly engages an opening in the housing 31. The compression spring 33 normally tends to urge the diaphragm 32 to the left, as viewed in the drawing, and the position of the stud may be altered so as to regulate the amount of force which the spring exerts upon the diaphragm 32. As seen in the drawings, the conduit 28 communicates with the interior of housing 31, thereby subjecting the inner surface of diaphragm 32 to venturi vacuum, while the outer surface of the diaphragm is subjected to atmospheric air pressure. Alternatively, the conduit 28 may be in communication with the engine intake passage 12 through a branch 29 whereby the interior of the housing 31 will he subjected to intake manifold vacuurn rather than venturi vacuum, in which case suitable modifications, cognizant to those skilled in the art, will have to be made. The diaphragm 32 is connected to a rod 36, which is, in turn, connected through an adjustable coupling 37 to a rod 38.

The carburetor 10 includes a pivotally supported throttle valve 39 for controlling communication between the carburetor and the intage passage. The throttle valve 39 either actuates directly, or, as shown, is connected by a mechanical linkage 40 to a switch 41, the arrangement being such that switch'41 will be moved to the closed position and retained therein whenever the throttle valve 39 is moved to and beyond a predetermined open position. The particular open position at which the throttle valve 39 will close the switch 41 will, of course, vary with different engines. However, for the purposes of the present invention, it will be assumed that the throttle valve 39 will close the switch 4]. whenever the throttle is opened 70, or more.

The switch 41 includes a switch blade 42, which is connected by a wire 43 to one terminal of a battery 44, the other terminal of which is connected to ground. The switch 41 also includes a contact 45. The contact 45 is connected by a wire 46 to a relay armature 47 of a relay 50. The movable relay armature 47 carries a contact 48, the armature 47 being spring biased to the right by a tension spring 49. The means for energizing relay 50 comprises a pair of coils and 70, which are arranged in electromagnetic, bucking relation. That is, the magnetic flux produced by the flow of current through coils and 60 buck, or oppose each other, so that the armature 47 will only be attracted when a predetermined current diflerential exists between coils 69 and 70. Thus, the relay 50 may be called a differential relay.

The contact 45 is also connected with a wire 51 which is connected to two circuits arranged in parallel relationship. One parallel circuit inclndes a manually variable resistor 61, which constitutes a calibration adjustment, the resistor being connected to wire 51 and serially connected with a variable resistor 62, which will be called an aging resistor. The ohmic value of resistor 62 varies with time. Structurally, the resistor 62 may comprise a sheet of plastic having dispersed thereon a thin metallic film of aluminum, the aluminum being electrostatically deposited on the plastic. The electrical resistance of the aluminum has been found to change with the passage of time, due to a chemical action. The two resistors 61 and 62 are serially connected with the bucking winding 6% and, thence, to ground through wire 55, these elements constituting one of the parallel circuits.

The other parallel circuit includes a variable resistor 71, the ohmic value of which varies with the humidity of the intake mixture. Thus, the resistor 71 comprises a potentiometer having a movable arm 72 connected to the wire 51, .the movable arm being pivoted at 73, and the other end thereof being connected to a link 74, which constitutes the component of a hair hygrometer, designated generally by the numeral 75. The hygrorneter 75 is of conventional design and includes a pair of human hairs 76 and 77, opposite ends of which are connected to a fixed support 78 and the link 74, the other end of the link 74 being connected by a spring 79 to a fixed support 80. structurally, the hygrometer 75 will be located so that the hairs 76 and 77 are subjected to the intake mixture such that during changes in the humidity of the intake mixture, the pointer 72 will be adjusted so as to vary the ohmic value of resistance 71 in the circuit. Preferably, the ohmic value will vary directly with respect to humidity of the intake mixture. The resistor 71 is serially connected to a variable resistor 81, the ohmic value of which varies with the temperature of the intake mixture. Preferably, the variable resistor 81 is of the type having a negative temperature coeflicient so that the ohmic value thereof varies inversely with temperature. That is, the ohmic value of the variable resistor 81 will decrease with an increase in temperature. The variable resistor 81 is connected to a wire 82, which is, in turn, connected to branch wires 83 and 84, which connect with segments of a non-linear variable resistor 85. The resistor 85 is shown divided and with an open circuit between segments thereof so as to illustrate its non-linear characteristic. The amount of resistance connected into the second parallel circuit is controlled by a movable arm 87, which is operatively connected to and positioned by the rod 38, the arm 87 being pivotally supported at 88. The arm 87 is also connected by a wire 89 to the coil 70 and, thence, to ground through wire 55.

Briefly, the hereinbefore described device operates to enrich the mixture by energizing solenoid 24 whenever the various parameters sense incipient detonation. The sensing circuits, aforedescribed are balanced against each other so that the two bucking coils 6i) and 70 of the relays 50 will not effect armature movement until a predetermined current differential exists in the two parallel circuits. The non-linear resistor 85 is designed to permit enrichment of the mixture at various ranges of speed. For example, with certain engines detonation may occur under certain conditions between engine speeds of 600 to 2000 R. P. M., and not occur beyond 2000 R. P. M. However, this same engine may have another detonation range starting at 3000 R. P. M. Thus, the resistor 85 is tailored to meet the specific operating characteristics of the engine with which the anti-detonating carburetor is to be used. Moreover, as humidity is more closely related to detonation than pressure and temperature, the

resistor 71 will have more effect in the one sensing circuit than will pressure and temperature.

Operation The anti-detonation device operates as follows. When the engine, not shown, is operating with the throttle valve 39 at an open position less than 50, the switch 41 will be open, and, accordingly, the sensing circuits will not be energized. However, as soon as the throttle valve 39 is moved to an open position of 50 or more, the switch 41 will be closed so as to energize the parallel sensing circuits. When the sensing circuits are energized, there may, or may not, be a suflicient current differential therebetween to actuate relay 50. However, if the several parameters are considered individually, the sensing circuits will operate in the following manner. The variable resistor 81 will sense incipient detonation as the temperature increases in the intake passage, thereby causing the ohmic value of the thermistor to decrease. Thus, the sensing circuits will be affected by a temperature increase since it will tend to cause a dilferential current flow in the two parallel circuits. A sufiicient temperature increase will cause a predetermined current differential so as to energize relay 5%, thereby effecting enrichment of the air-fuel mixture. Similarly, as venturi suction increases, or in the modified embodiment, as intake vacuum increases, the diaphragm 32 will be displaced. In so doing, the resistance of the one parallel sensing circuit will be changed so that engine speed by itself may cause a sufficient current differential in the circuits to actuate relay 50. When the arm 87 of the resistor 85 is in the open circuit position, one of the sensing circuits has an infinite resistance so that at this time the relay 5G will be energized and the mixture will be enriched irrespective of the various other parameters. However, this will only occur if the throttie is at a position wherein the switch 41 is closed.

The humidity responsive resistor 71 increases in ohmic value as the humidity of the intake mixture increases. Thus, if the humidity of the intake mixture is high, the resistor 71 may prevent the existence of a predetermined current differential in the sensing circuits even though the mixture temperature and/ or engine speed is in the critical range. This is feasible since high humidity of the air fuel mixture will tend to prevent detonation.

The aging resistor 62 will be of such a nature that the ohmic value thereof decreases with an elapse in time so as to be an effective measure of carbon accumulation in the engine which tends to promote engine detonation. However, the specific characteristics of the aging resistor will vary with different engines, and the relative effect of the aging resistor can be controlled by the calibrating resistor 61, which also can be used as a sensitivity setting for the entire sensing circuit.

What is claimed is as follows:

1. In an internal combustion engine having a carburetor and an intake passage, means to enrich the combustible mixture produced by said carburetor, and means for actuating said mixture enrichment means comprising a solenoid, a circuit for energizing said solenoid including a switch, a relay for closing said switch having a pair of windings arranged in bucxing relation, and means responsive to certain engine conditions indicative of incipient engine detonation for differentially energizing said windings so as to effect energization of said relay and said solenoid.

2. The combination with an internal combustion engine having a carburetor and an intake passage; of means for automatically enriching the combustible mixture produced by said carburetor and flowing through said intake manifold, comprising, a carburetor enrichment valve, means for actuating said valve so as to enrich said mixture, and means for controlling said valve actuating means including a relay, a pair of windings arranged in bucking relation for closing said relay and means responsive to certain engine conditions indicative of incipient engine detonation for differentially energizing said windings so as to close said relay.

3. In combination with an internal combustion engine having a carburetor comprising a fuel reservoir, a venturi, a fuel nozzle disposed in the venturi, and a main fuel orifice for admitting fuel from said reservoir to said nozzle, the combination including an auxiliary fuel orifice for admitting fuel to said nozzle, a valve for controlling communication between said fuel reservoir and said auxiliary orifice, and means responsive to certain engine conditions indicative of incipient engine detonation for opening said valve so as to enrich the mixture passing through said carburetor comprising a relay having a pair of energizing windings arranged in bucking relation and means responsive to incipient engine detonation for difierentially energizing said windings so as to close said relay.

4. In combination with an internal combustion engine having a carburetor comprising a fuel reservoir, a venturi, a fuel nozzle disposed in the venturi, and a main fuel orifice for admitting fuel from said reservoir to said nozzle, the combination including, an auxiliary fuel orifice for admitting fuel to said nozzle, a valve for controlling communication between said fuel reservoir and said auxiliary orifice, and means for opening said valve to enrich the mixture flowing through said carburetor in response to certain engine conditions indicative of incipient engine detonation, said last recited means including means responsive to elapsed time of engine operation.

5. In combination with an internal combustion engine having a carburetor comprising a fuel reservoir, a venturi, a fuel nozzle disposed in the venturi, and a main fuel orifice for admitting fuel from said reservoir to said nozzle, the combination including, an auxiliary fuel orifice for admitting fuel to said nozzle, a Y-connection constituting a passage for fuel from said reservoir to said nozzle, the main fuel orifice being disposed in one leg of the Y and the auxiliary fuel orifice being disposed in the other leg of the Y, a valve for controlling communication between said fuel reservoir and said auxiliary orifice, and means including a device responsive to elapsed time of engine operation for sensing certain engine conditions indicative of incipient engine detonation and operable to open said valve so as to enrich the mixture flowing through said carburetor.

6. The combination set forth in claim 5 wherein the valve actuating means comprises a solenoid and a differential relay for controlling the energization of said,

solenoid.

7. In combination with an internal combustion engine having a carburetor comprising a fuel reservoir, a venturi, a fuel nozzle disposed in the venturi, and a main fuel orifice for admitting fuel from said reservoir to said nozzle, the combination including, an auxiliary fuel orifice for admitting to said nozzle, a valve for controlling communication between said fuel reservoir and said auxiliary orifice, means for opening said valve so as to enrich the mixture flowing through said carburetor, and means controlling the operation of said valve actuating means comprising a differential relay having a pair of energizing windings arranged in bucking relation, and means responsive to certain engine conditions indicative of incipient engine detonation for differentially energizing said relays so as to effect energization of said relay and operation of said valve.

8. The combination with an internal combustion engine having an intake passage and a carburetor, said carburetor having a mixture passage formed with a venturi, a throttle valve in said mixture passage for controlling communication between said mixture passage and the intake manifold, a fuel reservoir, a fuel nozzle disposed in said venturi, and a main fuel orifice for admitting fuel from said reservoir to said nozzle; of means for preventing destructive engine detonation comprising, an auxiliary fuel orifice for admitting fuel to said nozzle, said auxiliary fuel orifice being submerged in said fuel reservoir, a valve for controlling communication between the fuel reservoir and said auxiliary orifice, a solenoid for opening said valve so as to cause enrichment of the mixture flowing through said passage, an energizing circuit for said solenoid including a differential relay having a pair of windings arranged in bucking relation, means responsive to certain engine conditions indicative of incipient engine detonation for effecting energization of said differential relay, and means for conditioning the sensing means for operation when said throttle valve is opened at least a predetermined amount.

9. The combination set forth in claim 8 wherein the sensing means comprises a pair of parallel circuits, one of said bucking relay windings being serially connected in each circuit.

10. The combination set forth in claim 9 wherein one of said parallel circuits includes a serially connected calibrating resistor and a variable resistor, the ohmic value of which varies with the passage of time.

11. The combination set forth in claim 9 wherein the other of said circuits includes three serially connected variable resistors, the ohmic value of one of said resistors varying with the humidity of the manifold mixture, the ohmic value of the second of said resistors varying with the temperature of said manifold mixture, and the ohmic value of the third of said resistors varying with engine speed.

References Cited in the file of this patent UNITED STATES PATENTS 2,388,669 Baker Nov. 13, 1945 

1. IN AN INTERNAL COMBUSTION ENGINE HAVING A CARBURETOR AND AN INTAKE PASSAGE, MEANS TO ENRICH THE COMBUSTIBLE MIXTURE PRODUCED BY SAID CARBURETOR, AND MEANS FOR ACTUATING SAID MIXTURE ENRICHMENT MEANS COMPRISING A SOLENOID, A CIRCUIT FOR ENERGIZING SAID SOLENOID INCLUDING A SWITCH, A RELAY FOR CLOSING SAID SWITCH HAVING A PAIR OF WINDINGS ARRANGED IN BUCKING RELATION; AND MEANS RESPONSIVE TO CERTAIN ENGINE CONDITIONS INDICATIVE OF INCIPIENT ENGINE DETONATION FOR DIFFERENTIALLY ENERGIZING SAID WINDINGS SO AS TO EFFECT ENERGIZATION OF SAID RELAY AND SAID SOLENOID. 